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RFID System
User’s Manual
Section 4
RF
Ta
g Serv
ic
e Life
Det
e
c
tion
Section 4
Functions
RF Tag Service Life Detection
The OVERWRITE COUNT CONTROL command (MDS/MDL) can be used to determine whether the Tag
overwrite limit has been exceeded. With the MDS command, the overwrite count is subtracted from the data in
the user-specified overwrite count control area to determine whether the number of overwrites has been
exceeded. The MDL command can also be used to determine whether the overwrite count (100,000 times)
has been exceeded. The MDL command for RF Tags with a maximum number of 100,000 overwrites.
MDS Command
The overwrite count control area consists of 3 bytes from
the start address. The decrement value from the
overwrite count is written in this area, and if this value is
0 (00 hex) an end code 76 will be given as a warning.
Therefore, to enable control of the number of overwrites,
the maximum number of overwrites must be written to
the overwrite count control area beforehand.
The user-specified number of overwrites can be set to up
to 16,700,000. The number of overwrites in the
specifications for EEPROM RF Tags, however, is
100,000 overwrites (0186A0 hex) at 25
°
C max., so be
sure to set the number of overwrites to 100,000 or lower
The number of overwrites is controlled using hexadeci-
mal values, and can be read using the READ command.
If the control area data is already 0, the control area
value will not be refreshed, and only a warning will be
returned as a response. When the refresh count is set as
00 hex, the count will not be updated, and only an overwrite count check will be performed.
For details on the command format, refer to
OVERWRITE COUNT CONTROL (MD S/L)
.
Example Using the OVERWRITE COUNT (MDS) Command
Example: When the three bytes from address 0010 (hex) are used as the overwrite count area.
1. The overwrite count initial value of 100,000
times is written in the control area.
“WTSTH100100186A0”
2. Enter the overwrite count of 5.
“MDSTS1001005”
A total of 5 times will be decremented from
100,000.
3. The accumulated count is 100,000 times.
When “MDSTS1001000” is executed, it will be
“MD7610” (overwrite count exceeded.)
3 bytes
Area start address
Upper digit
Middle digit
Lower digit
0010
0011
0012
86 hex
01 hex
A0 hex
0010
0011
0012
86 hex
9B hex
01 hex
0010
0011
0012
00 hex
00 hex
00 hex